Conversion of hydrocarbons



April 24, 1945. G. s. BUNHAM CONVERSION 0F HYDRocARBoNs INVENTOR 650625 J Dun/Nm? BY TISNEY llll Abb MS, wwk b NN Filed Aug. 9, 1941 bk SN IAII , vaporizer '1.

Patented Apr. 24, 1945 CONVERSION F HYDROCARBONS George S. Dunham, Merion, Pa., assigner to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Application August 9, 1941, Serial No. 406,102

6 Claims.

This invention has to do with the conversion of hydrocarbons by vapor phase cracking in the presence of a contact mass capable of catalyzing conversion of gas oil to gasoline. It is particularly concerned with the proper preparation of charging stocks for such processes.

Several important characteristics must be possessed by such charging stocks. The most important one, probably, is that they should contain no substantial amount of material boiling above about '700 F. since such material tends to lay down coke upon the cracking catalyst far in excess of that which is deposited by normal cracking of lower boiling charge constituents. A f urther quality requirement is that the charge be free, if possible, from materials already Within the gasoline boiling range, since such materials,

in this process, are merely so much inert gas,

which blanket the eectiveness of a proportionate amount of the catalyst without usually giving rise to any oiisettng benets. y

For maximum economy of operation it becomes necessary to prepare a maximum amount of charge from crude. This requirement runs contrary in many ways to the propertiesvdesired 'in the optimum charge stocks. The presently disclosed process is the result of extensive commercial study and experience with previously proposed processes, and is believed to be that one Amostdesirable for the usual crudes of mixed base or similar types in that it most completely meets the requirements of high recovery of charge from crude While maintaining high quality of such charge.

In order to readily understand the process of thisvinvention, reference is now made to the drawing attached hereto, the single gure of which f duced crude so produced, Vcontaining all of the gas oil, is forwarded by pump 3 and pipe il through heater coil 5 and discharged through pipe E into Vaporizer l, Vwhich is preferably equipped with some form of entrainment separatorv as indicated at, and which may even take the form of a fairly competent vaporizerffrac- 4 rate therefrom all materials heavierthah this desired charge, such heavier materials constituting la vaporizer tar 'to be Withdrawn through pipe I0. l

Overhead vapor from pipe 9 may be passed directly through pipe I I to a catalytic cracking operation indicated by vessel I2, or these vapors may be superheated by passage through coil heater I3. The choice here depends somewhat upon the nature of the crude, some crudes requiring vaporizer operation at temperatures too low for proper catalytic cracking, but many permitting vaporizer operationy at temperatures suiiiciently high for direct passage to the catalytic cracking step.

The catalytic cracking step indicated at I2 may -be the catalytic cracking process disclosed in the various patents oi" Eugene Houdry and associates or any similar one wherein gas oil is converted to gasoline in the presence of a Contact mass of generally clay-like character. In case the process of Houdry is used, it is to be understood that the .single catalyst -case shown at i2 is merely in- *o dicative, since a commercial process of bed-inu pors pass to fractionator i4, therein to be separated into an overhead product delivered through pipe I5 and condenser IB to receiver Il from which gas is discharged at. I8 and catalytical'ly cracked gasoline at i9. At a point on the side of tower I4 it is usual to take a. side cut of gas oil, commercially designated as light fuel oil, which Vis withdrawn by pipe 2u, cooled in 2l and disposed of through 22. From the bottom of fractionator I4 there is Withdrawn through pipe 23 a recycle stock, constituting all material emergent from catalytic cracking heavier than gasoline except that material removed as a side cut at 20. Even this removal is optional, subject to commercial demands, and the whole of the material heavier than gasoline may be withdrawn, if desired, through 23. The material withdrawn through 23 is forced by pump 24 through pipe 25 to join the reduced crude flowing through coil heater 5.

Referring now to vaporizer l, the vaporizer tar collected therein and withdrawn through pipe It is forced by pump 26 through coil heater 2l and there subjected to viscosity breaking conditions 'suitably chosen for the conversion of a maximum of material into a boiling range suitable for the catalytic cracking charge with a minimum conversion to materials within the gasoline boiling range, The transfer line stream from the operation is delivered into vaporizer-fractionator 28 (two separate chambers may be used if desired), lwherein all material of boiling point too high for rial as vapon'zer tar, passing the gas oil vapors t0 and through a catalytic vapor phase conversion in the presence of a contact mass capable of catalyzing the cracking of the gas oil to gasoline, separating the vapors from said catalytic cracking into gasoline and materials heavier than gasoline, withdrawing catalytically cracked gasoline from the system, returning at least a portion of the material resulting from the catalytic cracking which is heavier than gasoline, to mix with incoming reduced crude oil, passing the vaporizer tar to and through a viscosity breaking operation operated to convert a maximum of tar to gas oil while converting a minimum to thermally cracked gasoline, separating thevresults of the viscosity breaker process into thermally cracked gasoline, viscosity breaker gas oil and viscosity breaker tar, withdrawing thermally cracked gasoline and viscosity breaker tar from the system and adding the viscosity breaker gas oil to mix with the reduced crude oil.

4. A process for the conversion of hydrocarbons to gasoline by vaporV phase catalytic cracking, comprising removing from a crude oil all materials lighter than gas oil, adding to said retained crude oil which includes the gas oil, an amount of gas oil derived from a catalytic cracking process equal to at least 50% by volume of said crude gas oil, and an amount of gas oil derived from a viscosity breaking process equal to at least by volume of said crude gas oil, heating the mixture in the presence of steam, separating the mixture into gas oil vapor suitable for vapor phase catalytic cracking and heavier material, withdrawing the heavier material as vaporzer tar, passing the gas oil vapors to and through a catalytic vapor phase conversion step in the presence of a contact mass capable of catalyzing the cracking of the gas oil to gasoline, separating the vapors :from said catalytic cracking into gasoline and materials heavier than gasoline, withdrawing catalytically cracked gasoline from the system, returning at least a portion of the material resulting from the catalytic cracking winch is heavier than gasoline, to mix with incoming reduced crude oil, passing the vaporizer tar to and through a viscosity breaking operation operated to ccnvert a maximum of tar to gas oil while converting a minimum lto thermally cracked gasoline, separating the results of the viscosity breaker process into thermally cracked gasoline, viscosity breaker gas oil and viscosity breaker tar, withdrawing thermally cracked gasoline and viscosity breaker tar from the system and adding the viscosity l materials lighter than gas oil, adding to said re-l tained crude oil which includes the gas oil, an amount of gas oil derived from a catalytic cracking process, heating the mixture to a temperature in excess of 800 F. but less than 900 F. in the presence of steam, separating the mixture into gas oil vapor suitable for vapor phase catalytic cracking and heavier material, withdrawing the heavier material as vaporizer tar, passing the gas oil vapors to and through a catalytic vapor phase conversion step at a temperature of about 825 F. in the presence of a contact mass capable of catalyzing the cracking of the gas oil to gasoline, separating the vapors from said catalytic cracking into gasoline and materials heavier than gasoline, withdrawing catalytically cracked gasoline from the system, returning at least a portion of the material resulting from the catalytic cracking which is heavier than gasoline, to mix with incoming reduced crude oil, passing the vaporizer tar to and through a viscosity breaking operation at a temperature in the range from 880-928 F. operated to convert a maximum of tar to gas oil while converting a minimum to thermally cracked gasoline, separating the results of the viscosity breaker process into thermally cracked gasoline, viscosity breaker gas oil and viscosity breaker tar, withdrawing thermally cracked gasoline and viscosity breaker tar from the system and adding the viscosity breaker gas oil to mix with the reduced crude oil.

6. A process for the conversion of hydrocarbons to gasoline by vapor phase catalytic cracking, comprising removing from a crude oil all materials lighter than gas oil, adding to said retained crude oil which includes the gas oil, an amount of gas oil derived from a catalytic cracking process equal to at least 50% by volume of said crude gas oil, and an amount of gas oil derived from a viscosity breaking process equal to at least 5% by volume of said crude gas oil, heating the mixture to a temperature in excess of 800 F. but less than 900 F. in the presence of steam, separating the mixture into gas oil vapor 'suitable for vapor phase catalytic cracking and heavier material, withdrawing the heavier material as vaporizer tar, passing the gas oil vapors to and through a catalytic vapor phase conversion step in the presence of a contact mass capable of catalyzing the cracking of the gas oil to gasoline, separating the vapors from said catalytic cracking into gasoline and materials heavier than gasoline, withdrawing catalytically cracked gasoline from the system, returning at least a portion of the material resulting from the catalytic cracking which is heavier than gasoline, to mix with incoming reduced crude oil, passing the vaporizer tar to and through a viscosity breaking operation operated to convert a maximum of tar t0 gas oil while converting a minimum to thermally cracked gasoline, separating the results of the viscosity breaker process into thermally cracked gasoline, viscosity breaker gas oil and viscosity breaker tar, withdrawing thermally cracked gasoline and viscosity breaker tar from the system and adding the viscosity breaker gas oil to mix with the reduced crude oil.

GEORGE S. DUNHAM. 

